John j



Patented Dec. 16,1890.

I -l-| 4- 44+ l+ CIRCUITS.

J. J. OARTY.

(No Model.)

MEANS FOR REDUCING INDUGTIVE DISTURBANGES IN TELEPHONE circuits.

ATENT JOHN .T. CARTY, OF NEV YORK, .LT. A

MEANS FOR REDUCING INDUCTIVE DISTURBANCES IN TELEPHONE-CIRCUITS.

SPECIFICATION forming part of Letters Patent No. 442,856, dated December 16, 1890. I Application filed September 18, 1890. $erial No. 865,317. (No model.) I

To all whom it may con-corn:

Be it known that I, JOHN J. CARTY, residingtrical disturbances which beset telephonic circuits, and especially to those which are attributable to induction from other and parallel Experience has demonstrated that theseare largely due in many cases to electrostatic induction or to the varying influences of charge and discharge and to the redistribution and rearrangement of the former.

The object of my present invention is to improve telephonic transmission over metallic circuits by eliminating the effects of electrostatic induction. I do this by so arranging the disturbing-circuit that it shall be enabled to exercise an equal electrostatic effect upon both sides-that is to say, on both line-conductors-of the metallic circuit which is or which otherwise would be disturbed.

In the drawings which form a part of this specification, Figures 1 and 2 are diagrams illustrating the principle of compensation.

which is embodied in myinventiomand Figs. 3, at, and 5 are diagrams which show, respectively, different modes of practically carrying out the said invention.

In Fig. 1, A is the disturbing-wire, which, simply for illustration, I will consider as being discontinuous at the outer end and as being at a given moment charged to adefinite negative potential by the electrotome D, which intermits the current of the battery I) in a local circuit 0, within which the primary helix ofthe induction-coilI is included. The secondary helix 2' of said induction-coil is in the line-circuit, and the entire apparatus maybe regarded as the source of sound. The said negative charge on A of course tends to induce a substantially equal positive charge, indicated by the plus-symbol on the line-wire B of the parallel metallic circuitL, and consequently a negative charge of like amount on the more distant linear conductor C of the same circuit. Speaking conventionally, we may say that the electricity of the circuit L is decomposed, a positive charge being attracted to the side B nearest to the inducing charged wire, while a corresponding charge of negative sign is repelled to the'more distant conductingsnrface of C. This redistribution results, of course, in currents through telephones T and T producing noise correponding to the note given out by the electrotome, and if the disturbing-line A were engaged in telephonic transmission the telephones T and T would reproduce the speech transmitted over A. In Fig. 2 a similar arrangement is illustrated, but in addition thereto a remedial agency is disclosed. The metallic telephone-circuit L is identical with that shown in Fig. 1, the telephone T being included therein at one end and the telephone T at the other. The disturbing-conductor A, having an earth-terminal e and provided with the induction-coil I, through which vibratory impulses are thrown onto the line tending to produce a musical note and actually establishing thereon as long as the line is open, a varying potential, is now provided with an associate line-conductor A holding the same inductive relation to the conductor 0 of the metallic circuit L as does A to the conductor B thereof-that is, the wire A is run parallel to and for the same length as O and at the sane distance therefrom as A is from B. A cross-wire or connecting-conductor F, located at any suitable point of the line, unites A and'A Then these are joined, as shown, the disturbingwire being operative, no sound is heard either at T or T This is readily explained bya consideration of the conditions, for A being at all times at the same potential as A, acts with the sameforce on O thatA does on B, and While A does, indeed, tend at any given moment to attract a positive charge on B and to repel an equal and opposite charge to 0, it is also true that its associate conductor A electrified at the same moment to the same potential, tends to attract a positive charge to C and to repel an equal and opposite charge to B. The resultant effect is of course zero, or neutrality, or, as indicated by the arrows, the flow or rearrangement of electricity will be lateral and the telephones T and T will be silent.

Fi 3 shows a practical utilization of the extended on the other side of circuit 1 and in similarly adjacent proximity to conductor 9 of said circuit, and its other main conductor 70, being itself extended parallel with and in proximity to wirelof circuit 3, is in likemanner united by cross-wire q to thelateral or wing conductor msimilarlyextended inlike inductive relation to the'main wi-remof circuit It the'circuitsarelong, it will sometimes-be found advantageous to unite the'l'ateral to their respectivemain conductors by additional crossqvires, as indicatedv i'n' dotted:

lines or By thi'sarrangement thecircuits'=1,

2, and 3 are freed from disturbauce'due" to electrostatic induction or variation of charge.

The action of the compensating-wiresfand n islike that of a condenser; each wireacting asone plate. It will be apparent, therefore, that they maybe replaced by a series of condensers'distributed along the, line, their total capacity equaling the capacity of the compensating-wire which they replace. Fig. 4 shows a similar three-circuit. system balanced in this way by the substitution of condensers for the lateral wires f and n. The

circuits 1 2 3 each are metallic circuits, and

are collectively composed of the-wires g, h, j,

is, Z, and m. Insteadof the-lateral extensions of the central circuit,.I provide on each outer a series of con-- densers-M', each-having one of its-plates united by a wire- 2) or q to that Wire of the central side'ofgthe circuits 1 and a circuit to which it is nearest, the other plate of said condensers being in each instance united byawire'r to the outer wire of the side circuit 1 or 3, as the case may be.

Fig. 5 illustrates a modification of my invention wherein the com pensating-wi res f and Marc utilized as extra conductors for the middle-circuit 2, being joined thereto at one end at the points '0 andcw and at the other end-at thepoi'uts as and 2.

It isalsoapparent from a study of the drawingsthat not only is themiddle circuit-enabled'by the construction shown to act. inductively with. equal effect upon both. lines of either side circuit, but that-by a parity of reasoning such inductive influence as is ex ercised by either side circuit on the neighboring wire of the middle circuit will be exerted by means of the lateral extensionsby both conductors of said side circuits, respectively, one acting directly upon the main conductor ofsa-id middle circuit and the other acting through the parallel branch or lateral extension thereof.

Having now fullydescribed my invention and my mode of' preventing cross-talk (as the most common disturbance between telephonic metallic circuitsis technically termed) by means of the establishment of an electro--- static balance, I'claim- 1. .Three or more metallicelectric circuits central circuit and extended along'the more distant conductor of the side: circuits, as specified herein, whereby each conductouofthesaid central circuit is enabled to exercise equal and. like electrostaticind'uctiveeffects upon: both near and distant conductors 0t its adjacent side circuits, for thepurposes set forth.

2. Three or more metallic telephone-circuits extended parallel to each other, as described, one of the said circuits being arranged between the other two, branch or wing conductors extended on the outer. side of each of the outer circuits in likeinduct'ive proximity to the outer conductors thereof as are the two sides of the middle circuitto the respective inner conductors of the said two outer circuits, and cross connections uniting the-said branch conductor respectively to the-nearest conductorof the middle circuit, whereby eachof the said: branch conductors'is made a lateral extension of't-heniain condnct-orto which 1 it'is electrically connected, and whereby. both conductors of each side' circuit are brought into equal inductive proximity with the nearestconductorofthemiddle circuit, for the purposes described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 4th dayv of September, 1890.

JOHN J. CART-Y. Witnesses:

L. H. LANDON, J12, HERBERT LAWS \VEBB.

ICC 

